1. Field of Invention
The present invention relates to the improvement in a floating magnetic head used in a hard disk drive and, more particularly, to improvements in a floating magnetic head of the composite type.
2. Description of the Prior Art
A floating magnetic head of the composite type which has heretofore frequently been used is generally indicated by reference numeral 1 in FIG. 11. This floating magnetic head 1 comprises a slider 2 made of barium titanate or calcium titanate together with rails 3 and 4 disposed on opposite sides of the slider 2. The top surfaces of the rails 3 and 4 form floating surfaces.
One rail 3 has a slit of a given depth, the slit 5 extending in a direction perpendicular to the direction M in which a magnetic recording medium (not shown) moves. A magnetic head core 6 made of a ferromagnetic substance such as a ferrite is inserted in the slit 5. The magnetic head core 6 is rigidly mounted by sealing of glass or by other means.
Indicated by reference d is the track width. The slider 2 is provided with two cutouts 7 and 8 forming a window. A coil 9 is wound on one portion of the magnetic head core 6 which is exposed to the window.
In the conventional floating magnetic head 1 shown in FIG. 11, the magnetic head core 6 is treated as an independent part until it is inserted into the slit 5, and therefore, it has been difficult to reduce the thickness of the core below 100 microns without breakage. To cope with high frequency signals, the eddy current loss of the core must be made small and therefore the magnetic head core 6 must be made thinner. However, this thinning has been very difficult to accomplish.
Also, it has been necessary to measure the depth of a R/W(Read/Write) gap of the magnetic head core 6 sealed with glass. To adjust the depth of the R/W gap, it has been necessary to make a measurement obliquely via the glass inside the slit 5. In this case, the measurement is very much affected by the refractive index of the glass or local distortion in the glass.
In recent years, the recording track width d has been reduced below 10 microns. Therefore, the ratio of the amount of the glass filled in the top portion of the slit 5 to the recording track width increases. Consequently distortion due to differences in thermal expansion coefficients among the glass, the slider, and the magnetic head core 6 (often consisting of a ferrite) increases, thus deteriorating the magnetic characteristics of the magnetic head core 6.
Thus, to make the magnetic head core 6 cope with high frequency signals, the thickness of the head core 6 has to be reduced, and therefore, it is necessary to reduce the width of the slit 5. As a result, it has been difficult to make the slit beyond 1 mm in depth keeping the width less than 100 microns. If the thickness of the magnetic head core is decreased while keeping the slit wide, the amount of glass filled would be increased, thus further increasing the characteristic variations due to the differences in thermal expansion coefficients. Another problem is that it is difficult to fill the glass without creating a void between the slider 2 and the magnetic head core 6 and without producing bubbles.